The most common type of wind turbine is the three-bladed upwind horizontal-axis wind turbine (HAWT), in which the turbine rotor is at the front of the nacelle and facing the wind upstream of its supporting turbine tower.
There exist a number of alternative wind turbine designs. One example is the multi-rotor array type wind turbine.
EP1483501B1 discloses a multi-rotor array-type wind turbine in which a plurality of co-planar rotors are mounted to a common support structure. Such a configuration achieves economies of scale that can be obtained with a very large single rotor turbine, but avoids the associated drawbacks such as high blade mass, scaled up power electronic components and so on. However, although such a co-planer multi-rotor wind turbine has its advantages, it presents challenges to implement the concept in practice, particularly in how to control the multiple rotors to achieve optimum power production. EP1483501B1 approaches the control strategy by treating each wind turbine of the system as a separate item that is controlled individually. It is against this background that the invention has been devised.